1. Technical Field
The present disclosure relates to an array substrate for a digital X-ray detector, a digital X-ray detector including the same, and a method for manufacturing the same.
2. Discussion of the Related Art
With the rapid development of digital technology, a digital X-ray detector based on a thin film transistor (TFT) has recently been developed, and has rapidly come into medical use. The digital X-ray detector is an apparatus capable of detecting the transmission amount (e.g., transmissivity) of X-rays passing through a subject and displaying internal images of the subject on a display.
Generally, the digital X-ray detector may be classified into a direct digital X-ray detector for directly detecting X-rays and an indirect digital X-ray detector for indirectly detecting X-rays. The digital X-ray detector is generally designed to have several thousand or tens of thousands of pixels, or many more pixels according to the size or resolution thereof.
FIG. 1 is a cross-sectional view illustrating a single pixel in a related art indirect digital X-ray detector.
The indirect digital X-ray detector 1 may include a thin film transistor 20 over a substrate 10, a positive-intrinsic-negative (PIN) diode 30 connected to the thin film transistor 20, and a scintillator 50 over the PIN diode 30. The thin film transistor 20 includes a source 27, a drain 25, a channel region 23, and a gate region 21. When X-rays are emitted to the digital X-ray detector, the scintillator 50 converts the incident X-rays into visible light, such that the visible light is transmitted to the PIN diode 30 below the scintillator 50. The PIN diode 30 includes a lower electrode 31, a PIN layer 33, and an upper electrode 35.
The upper electrode 35 of the PIN diode 30 is connected to a bias electrode 45 through a contact hole 41 formed in a protective layer 40. The bias electrode 45 transmits a power-supply voltage to the PIN diode 30. Holes and electrons are represented as “h” and “e” in circles, respectively.
The visible light applied to the PIN diode 30 is re-converted into an electronic signal in a PIN layer 33. The electronic signal is converted into an image signal after passing through the thin film transistor 20 connected to the lower electrode 31 of the PIN diode 30, such that the resultant image signal is displayed on a display.
However, according to the related art structure, in which the upper electrode 35 of the PIN diode 30 is connected to the bias electrode 45 through the contact hole 41, contact resistance increases, such that a voltage drop or heat generation may occur. In addition, because the bias electrode is formed to have a larger size, the related art structure may cause damage in a fill factor (also called an “aperture ratio”) of the pixel as large as the increased bias electrode. In addition, a bias electrode is applied only to the upper electrode 35 located in the vicinity of the contact hole 41, resulting in occurrence of an irregular voltage within the upper electrode 35.